Prepare examples for v12 (#1382)

docs/examples/greeting.js

@@ -26,7 +26,7 @@ client.on('guildMemberAdd', member => {
   const channel = client.channels.get(channelID);
 
   // send the message, mentioning the member
-  channel.sendMessage(`Welcome to the server, ${member}!`);
+  channel.send(`Welcome to the server, ${member}!`);
 });
 
 // log our bot in

docs/examples/ping.js

@@ -22,7 +22,7 @@ client.on('message', message => {
   // if the message is "ping",
   if (message.content === 'ping') {
     // send "pong" to the same channel.
-    message.channel.sendMessage('pong');
+    message.channel.send('pong');
   }
 });
 

docs/examples/webhook.js

@@ -9,4 +9,4 @@ const Discord = require('discord.js');
 const hook = new Discord.WebhookClient('webhook id', 'webhook token');
 
 // send a message using the webhook
-hook.sendMessage('I am now alive!');
+hook.send('I am now alive!');